Follow-Up: Experiment With Low Speed for 3-Speed Circulator

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lsayre
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Stoker Coal Boiler: AHS S130 Coal Gun
Coal Size/Type: Blaschak Anthracite Pea
Other Heating: Resistance Boiler (13.5 KW), ComfortMax 75
Location: N/E Ohio, between Medina and Wadsworth

Post Sun. Jan. 11, 2015 7:41 am

In a different one of my own threads I (being somewhat off topic) mentioned that this winter I was experimenting with leaving my single Taco 00R 3-Speed circulator (these circulators are discontinued as of several years ago and have been replaced by the Taco 0015 3-Speed) on its low speed setting (as opposed to medium speed where I have had it since the onset in 2011), and I had promised a follow up.

My homes single largest zone has a calculated "friction head loss" (there is no static head loss experienced by a circulating pump) of 8.4 feet. Per the pump curves (3 of them, one for each speed) at 8.4 feet of head my 00R 3-Speed circulator will deliver 8.9 GPM of total flow into my 4 open zone valve loops when on its "medium" speed setting, but it can only deliver 5.8 GPM of flow with all 4 zone valves open at its "low" speed setting.

BTU's of delivery potential are equated to water flow by the "general" equation:
BTUH = GPM x Delta-T x 500

For 8.9 GPM of flow and 20 degrees of temperature drop (Delta-T) across each of my 4 zones baseboards this equation yields 89,000 BTUH, but for 5.8 GPM it yields only 58,000 BTUH. It formerly seemed logical to me that since my boiler is capable of a maximum output of somewhere around 95,000 BTUH the closest delivered heat energy match was the medium speed setting, which will deliver 89,000 BTUH against a head of 8.4 feet.

But I have subsequently determined that my homes actual "heat loss" is only about 46,000 BTUH. The bottom line is that based upon the homes heat loss the circulators lower speed should still move adequate BTU's to heat my home, and in doing so it should make for quieter flow and also save in electricity consumption and system wear and tear.

We have recently hit minus 5 degrees F. here, and due to this low temp I have now witnessed several cases of all 4 zones calling simultaneously (meaning all 4 zone valves open at the same time), so I can now report in this (my follow up) that the 4 zones of our house did in fact successfully maintain their T-Stat set temperatures with the circulator set on its lowest speed. I think I'll be leaving it on low speed unless someone can tell me why this is a bad idea.


Mikeeg02
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Stoker Coal Boiler: Axeman Anderson 130
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Location: Milroy, PA

Post Sun. Jan. 11, 2015 10:26 am

I recently did a similar thing with my house. My loop to my house is a P/S setup. My primary pump circulates ~9-10 gpm based on calculated friction loss, and time it takes for warm water to get back to the boiler.

My house secondary loop had an old B&G pump that was noisey (keeping for a spare) and I replaced it with a 3 speed Grundfos. My other option was a single speed 008 taco, but the grundfos uses less power on all settings, and flows more on the highest setting so I bought the more efficient one with options.

/back story

Medium speed had the same flow curve as the pump I replaced so I started there. Worked as advertised, but then I decided to see if slowing it down would cause more even heating in the house. (The last section before going to the pump is in the living room and it also has the most radiation, and is where the thermostat is located.) As the living room would be a few degrees warmer then the bedroom.

For me slowing it down made the bedroom closer to thermostat temperature, and also improved my return temperature to the boiler on the primary loop because the house loop was using approximately 8 gpm, and now is around 5. Same situation here where it's been 0 out and everything stays warm.

I would say if your staying warm, everything is keeping up, and slower gpm should also help make for longer heat cycles, or get you closer to continuous circulation, which typically is the most comfortable.

I'm not an expert builder on this but it seems to me that in the worst conditions (or your target system build point) you should be circulating continuously, especially if in the back of your mind, you know you have a little more in reserve for that freak winter cold nightmare that we all nevr pray for. (Turning up circulation speed.)

waldo lemieux
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Post Sun. Jan. 11, 2015 11:10 am

Larry,

Did you note the Delta t on the loops before and after the switch? Thats whats gonna tell the tale. Im guessing that the reason for your findings is that you have relatively short runs. I don't know your sq footage but I think I remember 1900? If so, 4 zones is generous (read good) and will allow for lower flow through the zone...... I think :gee: Thanx for the update

waldo

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lsayre
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Stoker Coal Boiler: AHS S130 Coal Gun
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Other Heating: Resistance Boiler (13.5 KW), ComfortMax 75
Location: N/E Ohio, between Medina and Wadsworth

Post Sun. Jan. 11, 2015 11:21 am

waldo lemieux wrote:Larry,

Did you note the Delta t on the loops before and after the switch? Thats whats gonna tell the tale. Im guessing that the reason for your findings is that you have relatively short runs. I don't know your sq footage but I think I remember 1900? If so, 4 zones is generous (read good) and will allow for lower flow through the zone...... I think :gee: Thanx for the update

waldo
The longest of my 4 zones has roughly 140 feet of pipe overall. I did not monitor the Delta-T, but you just inspired me. I just hooked up my remote barbecue thermomiter to the supply and return lines of the boiler. Waiting for a zone to call and fire the boiler presently. First I will monitor the main return line and then I will monitor the return lines on the individual loops.
Last edited by lsayre on Sun. Jan. 11, 2015 11:35 am, edited 1 time in total.

waldo lemieux
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Post Sun. Jan. 11, 2015 11:35 am

I could tell you were looking for something to do :) Too, what is the longest loop in terms of fintube ? Ima guess about 40% of the length???

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lsayre
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Stoker Coal Boiler: AHS S130 Coal Gun
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Other Heating: Resistance Boiler (13.5 KW), ComfortMax 75
Location: N/E Ohio, between Medina and Wadsworth

Post Sun. Jan. 11, 2015 11:51 am

waldo lemieux wrote:I could tell you were looking for something to do :) Too, what is the longest loop in terms of fintube ? Ima guess about 40% of the length???
Fintube covers about 33% of the longest loop (which is our bedrooms loop). It is presently calling and I'm watching supply and return now. Delta-T seems to be hovering at between 19 and 22 degrees now that it has stabilized (I'm guessing it took about 3-4 minutes to fully stabilize). Presently seeing 153 degrees on the return and 172 degrees on the supply.

Update: Now it is at 171 degrees on the supply and 151 degrees on the return. Boiler should fire at 170 degrees. Holding rock steady at 20 degrees Delta-T now.

Update #2: About 10 minutes into the T-Stat call and now I'm seeing 167 on the supply and 149 on the return. Boiler just fired. Supply and return just went to 165 and 147 respectively.... (no insulation on the probes, only duct tape).

Update #3: About 17 minutes into the call from the T-Stat and the zones temperature has been satisfied. Circulator is off. Boiler is still firing.

Update #4 : 20 minutes post the T-Stat call and the boiler just shut off at 180 degrees, but with no circulation post ~17 minutes this experiment has ended. For my single largest zone the Delta-T is pretty close to 20 degrees overall (+/- 2 degrees). Lucky for me no other zones jumped in with calls to confuse things.

BTW, the coldest temperature seen but briefly on the return line was 112 degrees, shortly after the T-Stat called and the circulator started up.

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lsayre
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Stoker Coal Boiler: AHS S130 Coal Gun
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Other Heating: Resistance Boiler (13.5 KW), ComfortMax 75
Location: N/E Ohio, between Medina and Wadsworth

Post Sun. Jan. 11, 2015 12:25 pm

Basement loop T-Stat just called and after stabilization I'm now seeing the same 20 degree to 22 degree Delta-T for that zone, with most of the time spent at 20 degrees Delta-T. Seems to be performing just like the bedroom loop.

Update: The boiler took no more than 10 minutes to hit 180 degrees and cut off for this call, which followed almost immediately on the heels of the previous call. Briefly hit 25 degrees of Delta-T when the boiler temp was rising rapidly toward the end of its stretch to get back to 180 degrees.

Again, I was lucky enough to not have another zone calling for heat during this run. Boy are these remote barbecue thermometers fun.

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lsayre
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Stoker Coal Boiler: AHS S130 Coal Gun
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Location: N/E Ohio, between Medina and Wadsworth

Post Sun. Jan. 11, 2015 12:46 pm

Can't believe my luck. The Living Room/Dining Room/Kitchen loop is calling for heat now. Same 20 to 22 degrees of Delta-T being observed. Same event that the boiler fires at 165 to 167 degrees as seen on the circulator outlet line (and at 170 as seen on the gauge on the boiler proper). All of these three zones are fairly close to being the same length overall (which is a benefit of having the boiler central to the home).

Update: The bedrooms loop T-Stat just called while the Living Room/Dining Room/Kitchen loop is still calling, and the Delta-T briefly went clear to perhaps 50 degrees when this first occurred. But with stabilization I'm now seeing about 25 to 27 degrees of Delta-T across 2 zones simultaneously calling (with 27 degrees being seemingly more the norm).

Clearly the Delta-T is increased with more than one zone calling for heat. But it seems as if my DPBV is perhaps accomplishing something here to level the playing field a bit, as the Delta-T did not settle in at 40 degrees across two zones calling at once (as I thought it might). 7 degrees of deviation from the ideal is better than 20 degrees of deviation from the ideal.


waldo lemieux
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Post Sun. Jan. 11, 2015 1:24 pm

Larry,

I am curious to know how much the deltas change from low speed to medium speed. I think there may be a number in there (boiler reserve?) that would be interesting.

waldo

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mozz
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Post Sun. Jan. 11, 2015 1:30 pm

Now, up boiler temp 10 degrees and repeat. :shock: :shock: :shock: 170? Geeze, with steam I am at 190 low 230 high on aquastat. Will going any lower or any higher actually save coal? You need one of Freddy's AA reducers, make the fire smaller. :cry:

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lsayre
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Stoker Coal Boiler: AHS S130 Coal Gun
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Location: N/E Ohio, between Medina and Wadsworth

Post Sun. Jan. 11, 2015 1:34 pm

waldo lemieux wrote:Larry,

I am curious to know how much the deltas change from low speed to medium speed. I think there may be a number in there (boiler reserve?) that would be interesting.

waldo
OK, circulator speed was just bumped up to medium. Standing by for heat calls.

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lsayre
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Stoker Coal Boiler: AHS S130 Coal Gun
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Other Heating: Resistance Boiler (13.5 KW), ComfortMax 75
Location: N/E Ohio, between Medina and Wadsworth

Post Sun. Jan. 11, 2015 2:07 pm

Circulator on medium speed. Basement T-Stat is calling. At boiler firing the outlet temp was 165 degrees and the return temp was 149 degrees. Delta-T at boiler firing = 16 degrees. With additional observation it seems to be closely maintaining a 16 to 18 degree Delta-T. This as opposed to a 20 to 22 degree Delta-T with the lower circulator speed. Call it 4 degrees less Delta-T on average.

Maximum Delta-T observed before stabilization = 60 degrees.

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lsayre
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Stoker Coal Boiler: AHS S130 Coal Gun
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Other Heating: Resistance Boiler (13.5 KW), ComfortMax 75
Location: N/E Ohio, between Medina and Wadsworth

Post Sun. Jan. 11, 2015 2:27 pm

Delta-T is similarly stabilized at 16 to 18 degrees for the bedroom loop calling solo with the circulator on medium speed. Again, call it 4 degrees less Delta-T on average.

Once again though the Delta-T oddly spikes to as much as 24-25 degrees only briefly right before fan cut-off when the boiler really gets steamrolling and cranking the heat out.

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lsayre
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Stoker Coal Boiler: AHS S130 Coal Gun
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Other Heating: Resistance Boiler (13.5 KW), ComfortMax 75
Location: N/E Ohio, between Medina and Wadsworth

Post Sun. Jan. 11, 2015 3:16 pm

OK, now for something completely different. The Living Room/Dining Room/Kitchen zone is calling and with the circulator set on medium speed it has stabilized at a Delta-T of between 29 and 33 degrees. Call it 31 degrees of Delta-T on average. Completely out of line with expectations. I've had to check it 4 times to assure that it is the only loop with an open zone valve, and that is in fact the case. I'm totally at a loss to explain this one.

I think I will return the circulator to low speed when this zones call is satisfied.

Mikeeg02
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Post Sun. Jan. 11, 2015 3:27 pm

When is the last time that zone called for heat? The longer it sits, the cooler it gets, the more heat it dissipates returning to radiant temperature. Hense why I believe what I took from Sting, the closer to continuous circulation the better. (Although I think he likes continuous, my take on it is the closer to continuous the better. ). Less temperature swings both in the room and at the boiler.


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